COAL AND PETROLEUM

OAL AND PETROLEUM

Can air, water and soil be exhausted

by human activities? You have already

studied about water in Class VII. Is water

a limitless resource?

In the light of the availability of

various resources in nature, natural

resources can be broadly classified

into two kinds:

(i) Inexhaustible Natural Resources:

These resources are present in unlimited

quantity in nature and are not likely to

be exhausted by human activities.

Examples are: sunlight, air.

(ii) Exhaustible Natural Resources:

The

amount of these resources in nature is

limited. They can be exhausted by

human activities. Examples of these

resources are forests, wildlife, minerals,

coal, petroleum, natural gas etc.

Activity 3.2

(It is a group activity)

Take some containers. Fill them

with popcorn/peanuts/roasted

gram/toffees. Divide students into

groups of seven each. Further divide

each group into three subgroups

containing 1, 2 and 4 students.

Label them as first, second

and third generation respectively.

e use various materials for our

basic needs. Some of them are

found in nature and some

have been made by human efforts.

Activity 3.1

Make a list of various materials used

by us in daily life and classify them

as natural and man-made.

Natural Man-made

Can we use all our

natural resources

forever ?

Does this list include air, water, soil

and minerals? Since all these are

obtained from nature, they are called

natural resources.

Rationalised-2023-24

These sub-groups represent the

consumers. As population is

growing, second and third

generations have larger number of

consumers.

Put one full container for each

group on a table. Ask consumers of

the first generation from each group

to consume eatables from the

container of their group. Now, ask

the second generation consumers

from each group to do the same. Ask

students to observe carefully the

availability of eatables in each

container. If some thing is left in the

containers, ask third generation

from each group to consume it. Now,

finally observe whether all the

consumers of the third generation

got the eatables or not. Also observe

if anything is still left in any of the

containers.

Assume that the eatables in the

container represent the total

availability of an exhausible natural

resource like coal, petroleum or

natural gas. Each group may have a

different consumption pattern. Are

the earlier generations of any group

too greedy? It may be that the earlier

generations in some groups were

concerned about the coming

generation(s) and left something for

them.

In this chapter we will learn about

some exhaustible natural resources

like coal, petroleum and natural gas.

These were formed from the dead

remains of living organisms (fossils).

So, these are all known as fossil

fuels.

3.1 Coal

You may have seen coal or heard about

it (Fig. 3.1). It is as hard as stone and is

black in colour.

Fig. 3.1: Coal

Coal is one of the fuels used to cook

food. Earlier, it was used in railway

engines to produce steam to run the

engine. It is also used in thermal power

plants to produce electricity. Coal is also

used as a fuel in various industries.

Story of Coal

Where do we get

coal from and how

is it formed?

About 300 million years ago the

earth had dense forests in low lying

wetland areas. Due to natural processes,

like flooding, these forests got buried

under the soil. As more soil deposited

over them, they were compressed. The

temperature also rose as they sank

deeper and deeper. Under high pressure

and high temperature, dead plants got

slowly converted to coal. As coal

contains mainly carbon, the slow

process of conversion of dead vegetation

into coal is called carbonisation.

Since

it was formed from the remains of

vegetation, coal is also called a fossil fuel.

A coal mine is shown in Fig. 3.2.

COAL AND PETROLEUM

Rationalised-2023-24

SCIENCE34

Fig. 3.2: A coal mine

Coal Gas

Coal gas is obtained during the

processing of coal to get coke. It is used

Coal gas was used for street lighting

for the first time in London in 1810

and in New York around 1820. Now a

days, it is used as a source of heat

rather than light.

These days, bitumen, a petroleum

product, is used in place of coal-tar

for metalling the roads.

Fig. 3.3: Coal tar

When heated in air, coal burns and

produces mainly carbon dioxide gas.

Coal is processed in industry to get

some useful products such as coke, coal

tar and coal gas.

Coke

It is a tough, porous and black

substance. It is an almost pure form of

carbon. Coke is used in the manufacture

of steel and in the extraction of many

metals.

Coal Tar

It is a black, thick liquid (Fig. 3.3) with

an unpleasant smell. It is a mixture of

about 200 substances. Products

obtained from coal tar are used as

starting materials for manufacturing

various substances used in everyday

life and in industry, like synthetic

dyes, drugs, explosives, perfumes,

plastics, paints, photographic materials,

roofing materials, etc. Interestingly,

naphthalene balls used to repel moths

and other insects are also obtained from

coal tar.

Rationalised-2023-24

COAL AND PETROLEUM

as a fuel in many industries situated

near the coal processing plants.

3.2 Petroleum

You know that petrol is used as a fuel in

light automobiles such as motor cycles/

scooters and cars. Heavy motor vehicles

like trucks and tractors run on diesel.

Petrol and diesel are obtained from a

natural resource called petroleum. The

word petroleum is derived from petra

(rock) and oleum (oil) as it is mined

from between the rocks under Earth as

shown in Fig. 3.4.

Do you know how petroleum is

formed?

Petroleum was formed from

organisms living in the sea. As these

organisms died, their bodies settled at

the bottom of the sea and got covered

with layers of sand and clay. Over

millions of years, absence of air, high

temperature and high pressure

Refining of Petroleum

Petroleum is a dark oily liquid. It has

an unpleasant odour. It is a mixture of

various constituents such as petroleum

gas, petrol, diesel, lubricating oil,

paraffin wax, etc. The process of

Fig. 3.4 : Petroleum and natural gas deposits

The world’s first oil well was drilled

in Pennsylvania, USA, in 1859. Eight

years later, in 1867, oil was struck

at Makum in Assam. In India, oil is

found in Assam, Gujarat, Mumbai

High and in the river basins of

Godavari and Krishna.

transformed the dead organisms into

petroleum and natural gas.

Look at Fig. 3.4. It shows the deposits

of petroleum and natural gas. You see

that the layer containing petroleum oil

and gas is above that of water. Why is it

so? Recall that oil and gas are lighter

than water and do not mix with it.

Wells

Gas

Oil

Water

Reservoir rock

Impervious

rock

Rationalised-2023-24

SCIENCE36

separating the various constituents/

fractions of petroleum is known as

refining. It is carried out in a petroleum

refinery (Fig. 3.5).

Various constituents of petroleum

and their uses are given in Table 3.1.

Many useful substances are obtained

from petroleum and natural gas.

These are termed as ‘Petrochemicals’.

These are used in the manufacture

of detergents, fibres (polyester, nylon,

acrylic etc.), polythene and other

man-made plastics. Hydrogen gas

obtained from natural gas, is used in

the production of fertilisers (urea).

Due to its great commercial

importance, petroleum is also called

‘black gold’.

3.3 Natural Gas

Natural gas is a very important fossil

fuel because it is easy to transport

through pipes. Natural gas is stored

under high pressure as compressed

natural gas (CNG). CNG is used for

power generation. It is now being used

Table 3.1 Various Constituents of Petroleum and their Uses

S.No. Constituents of Petroleum Uses

1. Petroleum Gas in Liquid form Fuel for home and industry

(LPG)

2. Petrol Motor fuel, aviation fuel, solvent for

dry cleaning

3. Kerosene Fuel for stoves, lamps and for jet aircrafts

4. Diesel Fuel for heavy motor vehicles, electric

generators

5. Lubricating oil Lubrication

6. Paraffin wax Ointments, candles, vaseline etc.

7. Bitumen Paints, road surfacing

Fig. 3.5: A petroleum refinery

Rationalised-2023-24

COAL AND PETROLEUM

as a fuel for transport vehicles because

it is less polluting. It is a cleaner fuel.

The great advantage of CNG is that

it can be used directly for burning in

homes and factories where it can be

supplied through pipes. Such a network

of pipelines exists in Vadodara (Gujarat),

some parts of Delhi and other places.

Natural gas is also used as a starting

material for the manufacture of a number

of chemicals and fertilisers. India has vast

reserves of natural gas. In our country,

natural gas has been found in Tripura,

Rajasthan, Maharashtra and in the

Krishna Godavari delta.

3.4 Some Natural Resources

are Limited

You have studied in the beginning of

the chapter that some natural resources

are exhaustible like fossil fuels, forests,

minerals etc.

You know that coal and petroleum

are fossil fuels. It required the dead

organisms millions of years to get

converted into these fuels. On the

other hand, the known reserves of

these will last only a few hundred

years. Moreover, burning of these

fuels is a major cause of air pollution.

Their use is also linked to global

warming. It is therefore necessary that

we use these fuels only when

absolutely necessary. This will result

in better environment, smaller risk of

global warming and their availability

for a longer period of time.

In India, the Petroleum Conservation

Research Association (PCRA) advises

people how to save petrol/diesel while

driving. Their tips are

l drive at a constant and moderate

speed as far as possible,

l switch off the engine at traffic lights

or at a place where you have to wait,

l ensure correct tyre pressure.

l ensure regular maintenance of the

vehicle.

Can coal, petroleum

and natural gas be

prepared in the

laboratory from dead

organisms?

No. Their

formation is a very

slow process and

conditions for

their formation

cannot be created

in the laboratory.

Rationalised-2023-24

SCIENCE38

KEYWORDS KEYWORDS

KEYWORDS

COAL

COAL GAS

COAL TAR

COKE

FOSSIL FUEL

NATURAL GAS

PETROLEUM

REFINERY

WHAT YOU HAVE LEARNT WHAT YOU HAVE LEARNT

WHAT YOU HAVE LEARNT

Ü Coal, petroleum and natural gas are fossil

fuels.

Ü Fossil fuels were formed from the dead remains

of living organisms millions of years ago.

Ü Fossil fuels are exhaustible resources.

Ü Coke, coal tar and coal gas are the products

of coal.

Ü Petroleum gas, petrol, diesel, kerosene,

paraffin wax, lubricating oil are obtained by

refining petroleum.

Ü Coal and petroleum resources are limited. We

should use them judiciously.

Exercises

1. What are the advantages of using CNG and LPG as fuels?

2. Name the petroleum product used for surfacing of roads.

3. Describe how coal is formed from dead vegetation. What is this process

called?

4. Fill in the blanks.

(a) Fossil fuels are , and .

(b) Process of separation of different constituents from petroleum is

called .

5. Tick True/False against the following statements.

(a) Fossil fuels can be made in the laboratory. (T/F)

(b) CNG is more polluting fuel than petrol. (T/F)

(d) Coal tar is a mixture of various substances. (T/F)

(e) Kerosene is not a fossil fuel. (T/F)

6. Explain why fossil fuels are exhaustible natural resources.

Rationalised-2023-24

COAL AND PETROLEUM

7. Describe characteristics and uses of coke.

8. Explain the process of formation of petroleum.

9. The following Table shows the total power shortage in India from

1991–1997. Show the data in the form of a graph. Plot shortage percentage

for the years on the Y-axis and the year on the X-axis.

S. No. Year Shortage (%)

1 1991 7.9

2 1992 7.8

3 1993 8.3

4 1994 7.4

5 1995 7.1

6 1996 9.2

7 1997 11.5

E X E R C I S E S

Extended Learning — Activities and Projects

1. Get an outline map of India. Mark the places in the map where

coal, petroleum and natural gas are found. Show the places where

petroleum refineries are situated.

2. Choose any five families of your neighbourhood. Enquire whether

their energy consumption (coal, gas, electricity, petrol, kerosene)

has increased or decreased in the last five years. Enquire also about

the measures they adopt to conserve energy.

3. Find out the location of major thermal power plants in India. What

could be the reasons for their being located at those places?

For more information, visit:

l www.energyarchive.ca.gov

l web.ccsd.k12.wy.us

l web.pcra.org

Rationalised-2023-24